Coating of Crystalline Nuclear Waste Forms to Improve Inertness

Microspheres of a crystalline waste form prepared by sol‐gel processing were successfully coated with layers of pyrolytic carbon and silicon carbide to isolate the radioactive wastes from the biosphere. A separate process for cesium immobilization was developed, which loads 5 wt% Cs onto zeolite particles for subsequent coating. Pyrolytic carbon‐coated particles showed leach rates =2 to 4 orders of magnitude less than the candidate reference borosilicate glass waste form. Aqueous leach‐test results of coated waste forms were below detection limits of such sensitive analytical techniques as atomic absorption and inductively coupled plasma atomic emission.